I have never got into tachyon studies Bill S for a few simple reasons.

If they exist there universe is completely incompatable to ours it's like discussing the living conditions on a planet 50 billion light years from Earth to me.

Remember in there own universe I suspect time would move completely normal to them its only in our world that time would appear to go backwards. Thus the want to reverse the laws of physics is almost certainly incorrect. My guess would be they will be the same in there own world I mean if we simply rewite a new speed for C = 100x10E8 m/sec rather than 3x10E8 as the speed of light no real physics changes.

The speed of sound sort of shares this relationship with speed of light on earth you see a lightning bolt long before you hear it.

I think you are overcooking the reality it shouldn't be much more complicated than the speed of sound versus speed of light.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.